Radiant energy suppressor

ABSTRACT

Three concentric circular cylinders having a common vertical axis form an assembly which bolts to the louvered top of the heat engine enclosure of a military vehicle. The inner cylinder receives the tailpipe of the exhaust system and terminates in a horizontal plane above the tailpipe end. The outer cylinder terminates in a second horizontal plane above the first plane. The intermediate cylinder lies between the two horizontal planes. The annular spaces between the cylinders are open-ended for the upward flow of cooling air through the spaces. The intermediate cylinder substantially narrows the cone of visibility of heated interior surfaces to infrared radiation sensors.

United States Patent [191 Renius et al.

[111 3,817,030 June 18, 1974 RADIANT ENERGY SUPPRESSOR Inventors: Otto Renius, Rochester; Wilbert W.

Bremerkamp, Warren, both of Mich.

Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

Filed: June 26, 1973 Appl. No.: 373,829

US. Cl 60/271, 60/39.5, 60/271,

239/1273 Int. Cl. F0ln 7/20 Field of Search 60/271, 269, 264, 39.5,

[5 7] ABSTRACT Three concentric circular cylinders having a common vertical axis fonn an assembly which bolts to the louvered top of the heat engine enclosure of a military vehicle. The inner cylinder receives the tailpipe of the exhaust system and terminates in a horizontal plane above the tailpipe end. The outer cylinder terminates in a second horizontal plane above the first plane. The intermediate cylinder lies between the two horizontal planes. The annular spaces between the cylinders are open-ended for the upward flow of cooling air through the spaces. The intermediate cylinder substantially [56] References Cited narrows the cone of visibility of heated interior sur- UNITED STATES PATENTS faces to infrared radiation sensors. 3,210,934 l0/l965 Smale 60/265 3,693,880 9/1972 Versaw et al. 239/1273 8 Claims, 2 Drawing Flgllres L g H I 30 I Y W 1 Y 7'? 9 X I 2 X f 0 l L r k /a t 2 J. V 2

l P l I I I t I l l l /6 LI//\ /WJ HEAT L Z\, ENGINE EXHAUST EFFLUENT' PATENTED N1 m4- 3'817'030 SHEET 2 BF 2 i1 8 RADIANT ENERGY SUPPRESSOR The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposeswithout payment to us of any royalty thereon. I

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a device to suppress radiant energy emanating from a heat source to minimize detection by hostile heat sensors. More specifically, the invention relates to a device for the exhaust systems of heat engines which serve as primary power plants for military vehicles, to prevent long distance detection of the heat source by enemy fire control devices.

2. Prior Art Devices of the general type here under consideration are concerned primarily with shielding the exhaust as a sound or as a light source, or they are so restrictive as to build up back pressure so as to interfere with efficient operation of the power source.

SUMMARY OF THE INVENTION The invention is a device to suppress infrared radiant energy of heat engine exhaust systems and is adapted to receive exhaust gas from the tailpipe of the exhaust system. The radiation suppressant device is mounted with its flow axis vertical, and has an exhaust receiver pipewhich receives gas from the tailpipe. A heat shield coaxially surrounds the exhaust receiver pipe and is spaced therefrom to form an annular space which is open at both ends. The exhaust receiver pipe terminates atTa horizontal plane that is above and spaced from the end of the tailpipe, and the heat shield terminates at a second horizontal plane above and spaced from the first plane. An air-to-ground shroud or shield, also coaxial with the exhaust receiver pipe, lies between the two planes and is smaller than the heat shield and larger than the exhaust receiver pipe, forming with the heat shield an annular space which is also open at both ends. The air-to-ground shield substantially narrows the cone of visibility to reconnaissance devices such as infrared or optical (orboth) types.

It is accordingly an object of the invention to minimize the heat signature of the (usually automotive) heat engine to terminal homing, surveillance, and target acquisition devices, all of which can be sensitive to infrared radiation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side view, partly in elevation and partly in section, of the invention, being a view substantially on line I l of FIG. 2 and FIG. 2 is largely a bottom plan view which cuts through the exhaust receiver pipe, being a view in section on line 2 2 of FIG. 1.

DETAILED DESCRIPTION OF INVENTION In FIG. 1, a purely schematic representation of a heat engine 2 is shown connected to discharge its exhaust effiuent through a suitable conventional conduit 4 and thence to a muffler 6 which is provided at its discharge end with a tailpipe 8. In the illustrated embodiment the muffler and tailpipe are oriented so that the flow axis is vertical. The heat engine is at least partially enclosed in an enclosure usually called an engine compartment,

' at 14 and comprises, basically, three circular cylinders concentrically held together and having their common flow axis vertically disposed, which herein is coincident with the flow axis of tailpipe 8.

More specifically, an exhaust receiver pipe 16 has a sliding or telescopic fit with, and surrounds, the upper end of muffler tailpipe 8. Pipe 16 terminates at its upper end at a horizontal plane shown at X X in FIG.

1, which is located above and spaced from the end of tailpipe 8. Pipe 16 is one of the aforesaid three circular cylinders, of which a second is a heat shield 18; shield 18 is coaxial with and larger than exhaust receiver pipe 16 and forms an annular space 20 therewith. The upper end 22 of shield 18 is shown at a second horizontal plane Y Y which lies above and is spaced from plane X X.

The third concentric circular cylinder is an air-toground shield (or shroud) 24 which is larger than exhaust receiver pipe 16, smaller than heat shield 18, and extends between planes X X and Y Y, being here shown as actually or substantially terminating in those planes. Shield 24 is held in place on the upper end of pipe 16 by a pair of crossed rods 26, 28 which are preferably welded to pipe 16 and shield 24. The two shields 18 and 24 define an annular space 30 between them.

recessed as at 40 in order to open the annular space 20 I to the entry of cooling air, most of which is forced upward through the louvered hood by the conventional cooling system fan (not shown) in the engine compartment.

Particular attention is now directed to the left side of FIG. 1 for a discussion of the cone of visibility with which this invention is concerned. Most of the intelligence gathered by hostile forces is the product of infrared devices which sense heat sources and then zero in on such sources, and such devices are carried by manned or drone reconnaissance aircraft. The object of the enemy is topick up" United States units from as far away as possible. Conversely, US. forces seek to prevent detection from afar, because reconnaissance craft are reluctant to pass directly overhead.

Infrared devices used to detect heat sources require rectly overhead to be effective, the enemys heat detection capability is rendered virtually ineffectual.

In FIG. 1, line OH forms an angle A with the vertical V. Angle 2A is then the vertex angle of the cone of visibility for hostile reconnaissance if the suppression device is not equipped with the air-to-ground shield 24. On the other hand, line PL forms an angle B with the vertical, PV, and angle 2B is the vertex angle of the cone of visibility for a device having the air-to-ground shield 24. It is evident in FIG. 1 that angle 28 is much smaller than angle 2A, so that a device equipped with shield 24 is much less likely to be detected by enemy sensors in time to be effective.

lt is noted that hot exhaust gases should not impinge upon the air-to-ground shield 24 to avoid making it such a heated surface as would set off hostile sensors. This is accomplished by making shield 24 large enough radially and short enough vertically to avoid or minimize such impingement, while simultaneously cooling the exhaust gases, and confining them by an annulus of cooling air rising from annular space 30, as well as air from annulus 20 passing upward on the inside of shield 24, which also helps to keep exhaust gases from impinging on shield 24.

OPERATlON The operation of the device need only be summarized at this point. Air forced upward through the hood louvers by the engine cooling fan enters annulus 20 and cools exhaust receiver pipe 16, cooling the exhaust gases flowing upward and out inside pipe 16. At the same time, the cone of visibility is substantially reduced in size to the extent that the surfaces that are exposed to hostile heat sensors cannot be in a position to see those surfaces until the sensors are so close to overhead as to be ineffective for warning purposes at the same time that they are more vulnerable to anti-aircraft fire.

It is also noted that crossed rods 26 and 28 serve a purpose beyond that of supporting the air-to-ground shield, which purpose is to keep out explosives (e.g., hand grenades) which ground troops might try to drop down into the engine compartment.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What is claimed is:

l. A device to suppress the radiant energy emanating from the discharge conduit of the exhaust system of a heat engine comprising:

a. a second conduit engageable with the discharge conduit and terminating at a plane spaced from the discharge conduit;

b. a heat shield coaxial with the second conduit,

i. terminating at a second plane which is farther from the discharge conduit than the first-named plane, and

ii. forming with the second conduit an annular space open at both ends; and

c. an air-to-ground shield,

i. coaxial with the second conduit,

ii. larger than the second conduit and smaller than the heat shield and forming with the heat shield an annular space, and

iii. extending longitudinally between the spaced planes.

2. A device to suppress the radiant energy emanating from the tailpipe of the exhaust system of an enclosed heat engine comprising:

a. an exhaust receiver pipe engageable with the taili. having a substantially vertical flow axis, and

ii. terminating at a horizontal plane above and spaced from the tailpipe;

b. a heat shield coaxial with the exhaust receiver i. terminating at a second horizontal plane above and spaced from the first plane, and

ii. forming with the exhaust receiver pipe an annular space which is open at both ends;

c. means for mounting the exhaust receiver pipe and the heat shield on the enclosure of the enclosed heat engine; and

d. an air-to-ground shield,

i. larger than the exhaust receiver pipe and smaller than the heat shield and forming with the latter an annular space,

ii. extending longitudinally between the two spaced horizontal planes, and

iii. coaxial with the exhaust receiver pipe.

3. A device as in claim 2, and means mounting the air-to-ground shield at'the upper end of the exhaust receiver pipe and comprising a pair of elongated members secured intermediate their ends to said upper end and having their ends secured to the air-to-ground shield.

4. A device as in claim 3, wherein the means for mounting the exhaust receiver pipe and the heat shield comprises a centrally-apertured bracket adapted to receive the exhaust receiver pipe and having a plurality of ears adapted to be secured to the engine enclosure.

5. A device as in claim 2, wherein the means for mounting the exhaust receiver pipe and the heat shield comprises a centrally-apertured bracket adapted to receive the exhaust receiver pipe and having a plurality of ears adapted to be secured to the engine enclosure.

6. A device as in claim 1, and means to keep explosives from passing through the air-to-ground shield.

7. A device as in claim 6, wherein the last-named means comprises a pair of elongated members disposed substantially in the first-named plane.

8. A device as in claim 7, the elongated members being secured to the second conduit and to the air-toground shield to hold the latter in place. 

1. A device to suppress the radiant energy emanating from the discharge conduit of the exhaust system of a heat engine comprising: a. a second conduit engageable with the discharge conduit and terminating at a plane spaced from the discharge conduit; b. a heat shield coaxial with the second conduit, i. terminating at a second plane which is farther from the discharge conduit than the first-named plane, and ii. forming with the second conduit an annular space open at both ends; and c. an air-to-ground shield, i. coaxial with the second conduit, ii. larger than the second conduit and smaller than the heat shield and forming with the heat shield an annular space, and iii. extending longitudinally between the spaced planes.
 2. A device to suppress the radiant energy emanating from the tailpipe of the exhaust system of an enclosed heat engine comprising: a. an exhaust receiver pipe engageable with the tailpipe, i. having a substantially vertical flow axis, and ii. terminating at a horizontal plane above and spaced from the tailpipe; b. a heat shield coaxial with the exhaust receiver pipe, i. terminating at a second horizontal plane above and spaced from the first plane, and ii. forming with the exhaust receiver pipe an annular space which is open at both ends; c. means for mounting the exhaust receiver pipe and the heat shield on the enclosure of the enclosed heat engine; and d. an air-to-ground shield, i. larger than the exhaust receiver pipe and smaller than the heat shield and forming with the latter an annular space, ii. extending longitudinally between the two spaced horizontal planes, and iii. coaxial with the exhaust receiver pipe.
 3. A device as in claim 2, and means mounting the air-to-ground shield at the upper end of the exhaust receiver pipe and comprising a pair of elongated members secured intermediate their ends to said upper end and having their ends secured to the air-to-ground shield.
 4. A device as in claim 3, wherein the means for mounting the exhaust receiver pipe and the heat shield comprises a centrally-apertured bracket adapted to receive the exhaust receiver pipe and having a plurality of ears adapted to be secured to the engine enclosure.
 5. A device as in claim 2, wherein the means for mounting the exhaust receiver pipe and the heat shield comprises a centrally-apertured bracket adapted to receive the exhaust receiver pipe and having a plurality of ears adapted to be secured to the engine enclosure.
 6. A device as in claim 1, and means to keep explosives from passing through the air-to-ground shield.
 7. A device as in claim 6, wherein the last-named means comprises a pair of elongated members disposed substantially in the first-named plane.
 8. A device as in claim 7, the elongated members being secured to the second conduit and to the air-to-ground shield to hold the latter in place. 